Molecular Epidemiology of A/H3N2 and A/H1N1 Influenza Virus during a Single Epidemic Season in the United States
Author Summary
This study is the first of its kind to reconstruct the spread
of an epidemic of influenza A virus across a single country,
in this case the United States. In contrast to a single viral
lineage spreading across this country, a phylogenetic
analysis of the whole-genome sequences of more than 300
influenza A viruses of the A/H1N1 and A/H3N2 subtypes
sampled from the 2006?2007 epidemic season reveals that
multiple phenotypically and antigenically distinct viral
lineages of entered and co-circulated in the US during this
time. Furthermore, the widespread co-circulation of
multiple lineages, even in geographically remote localities,
allowed for frequent reassortment between influenza A
viruses of the same subtype. Through reassortment, a
minor lineage of A/H3N2 viruses surprisingly re-acquired
sensitivity to the adamantane class of antiviral drugs, and a
new A/H1N1 antigenic variant emerged that later became
globally dominant. In sum, these results highlight the
complexity of the spread of influenza A virus in time and
space, and highlight the need for intensified global
surveillance involving whole-genome sequence data.
http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1000133
Author Summary
This study is the first of its kind to reconstruct the spread
of an epidemic of influenza A virus across a single country,
in this case the United States. In contrast to a single viral
lineage spreading across this country, a phylogenetic
analysis of the whole-genome sequences of more than 300
influenza A viruses of the A/H1N1 and A/H3N2 subtypes
sampled from the 2006?2007 epidemic season reveals that
multiple phenotypically and antigenically distinct viral
lineages of entered and co-circulated in the US during this
time. Furthermore, the widespread co-circulation of
multiple lineages, even in geographically remote localities,
allowed for frequent reassortment between influenza A
viruses of the same subtype. Through reassortment, a
minor lineage of A/H3N2 viruses surprisingly re-acquired
sensitivity to the adamantane class of antiviral drugs, and a
new A/H1N1 antigenic variant emerged that later became
globally dominant. In sum, these results highlight the
complexity of the spread of influenza A virus in time and
space, and highlight the need for intensified global
surveillance involving whole-genome sequence data.
http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1000133